Documents U.S. Pat. No. 7,036,929, U.S. Pat. No. 3,628,854, and FR 2 924 819 disclose a thin flexible ophthalmic lens suitable for sticking onto a lens of a pair of eyeglasses. The flexible lens enables the optical characteristics of the pair of eyeglasses to be modified at little expense by adding supplementary optical correction to the eyeglass lens, e.g. because the wearer's visual acuity has diminished. The flexible lens is thus generally put into place on the eyeglass lens after it has already been machined and assembled in the pair of eyeglasses. It is therefore appropriate to begin by cutting the flexible lens so as to bring its outline to the desired shape, i.e. to the shape of the eyeglass lens.
The difficulty is that using an eyeglass lens grinder for machining the flexible lens is not possible because said lens is too flexible. If the flexible lens were to be blocked in a grinder, then the grindwheel would cause the flexible lens to fold instead of machining it.
The solution used at present for bringing the flexible lens to the shape of the eyeglass lens consists in cutting the flexible lens using a pair of scissors or a cutter. It will readily be understood that the accuracy of such a method is approximate and depends to a large extent on the skill of the optician.
That solution is also not viable for flexible lenses that present cylindrical and/or prismatic optical powers. Such lenses need to be oriented angularly very accurately relative to the eyeglass lenses in order to perform correctly the optical functions for which they are designed, and this cannot be achieved manually except by accepting accuracy that is very low and therefore giving rise to poor optical comfort.